Lifting device

ABSTRACT

A lifting device provided with a hydraulic unit having a pressure cylinder and a piston rod and a transverse shaft rotatably mounted on the upper end of the piston rod and having affixed thereto two fixed cogwheels, one having a larger diameter than the other, wherein the one cog wheel engages in a fixed rack and the second cog wheel engages in a rack movable vertically with a carrier device. The carrier device is movable vertically along a vertical rail or the like.

I Umted States Patent [151 3,674,240 Larsson 1 July 4, 1972 LIFTING DEVICE FOREIGN PATENTS OR APPLICATIONS [72] inventor: Bertil Ivar Torsten Larsson, Norrgard S- 1,248,254 8/1967 Germany 187/19 330, I0 Bredaryd, Sweden Primary Examiner-Othell M. Simpson [22] 1969 Attorney-Robert E. Burns [2]] Appl. No.1 884,991

[57] ABSTRACT |3U| Foreign Application Priorit D t A lifting device provided with a hydraulic unit having a pressure cylinder and a piston rod and a transverse shaft rotatably heh. I}, I969 Sweden ..l959/69 mounted on the upper end of the piston rod and having ffi d thereto two fixed cogwheels, one having a larger diameter U-S- Cl- ...254/95, R than the other wherein the one cog wheel engages in a fixed [5 l I Cl. l ra k and the e ond cog wheel engages in a rack movable ver. Fleld Search 187/9, 19; 212/55; 254/95, tically with a carrier device. The carrier device is movable ver- 254/97, 2, 612, 59, 66; 92/1 tically along a vertical rail or the like.

[56] References Cited 8 Claims, 3 Drawing Figures UNITED STATES PATENTS McNeeley 1 87/9 PATENTEDJUL 41972 sum 1 or 3 urrnvc DEVICE BACKGROUND OF THE INVENTION The present invention relates to a device provided with a hydraulic unit having a pressure cylinder and piston rod, for raising and lowering a fixed load, such as for instance a chair for dental treatment or for attending the sick. The present invention also relates to a lifting device for load-carrying vehicles for moving the load vertically, for instance for lifter trucks or the like, or for stationary use in store-rooms or the like when goods are to be moved vertically between different floors or shelves.

One previously known and frequently met construction is the telescopic hydraulic lifter, with a large number of telescopic sections permitting a large lift height. This type of lifting device however very readily becomes unstable, often necessitating a complicated framework consisting of means for supporting both the carrier device and the telescopic sections. With telescopic hydraulic lifters the telescopic tubes must also be disposed directly below the carrier device, so that the force is applied substantially vertically, and hence the lifting device must be disposed in a plane under the ground surface if a load has to be lifted from the said ground surface. The construction height of this lifting device thus corresponds to the height of the hydraulic lifter in the folded position plus the distance travelled by the device. For small travelling distances the height of previously known constructions is thus relatively great. Also lifting is effected by stages and jerkily when each individual telescopic tube is withdrawn, which has a very upsetting effect.

SUMMARY OF THE INVENTION The object of the present invention is to provide a lifting device with a very low height, Le. a height which almost corresponds to that of its travel.

The present invention is characterized by a transverse shaft rotatably mounted on the upper end of the piston rod and having affixed thereto two fixed cog wheels; one having a larger diameter than the other, wherein the one cog wheel engages in a fixed rack and the other cog wheel engages in a rack movable vertically with a carrier device. The carrier device is movable vertically along a vertical rail or the like.

Other features of the invention will appear from the subclaims below.

The transmission of movement of a hydraulic piston as provided by the invention ensures inter alia a steady and smooth lifting movement, which is of great advantage in lifting patients in treatment chairs, on operating tables etc. Starting with a normal hydraulic piston with a certain stroke length and a certain lifting capacity, a lifting device can be provided for a given purpose with any desired lifting height and capacity, by choice of a certain diameter for each of the two cog wheels. In addition to the high loading capacities usually sought for the larger lifting heights, for certain fields of use a lesser lifting height and at the same time a greater load capacity than is possible for the hydraulic piston along may be necessary; this is achieved by choosing a cog wheel to cooperate with the fixed rack which is of greater diameter than that cooperating with the movable rack.

Should extremely large lifting heights be desired, one or more additional gear mechanisms may be disposed in series, wherein the movable rack cooperates with two cog wheels disposed on a transverse axis, said cog wheels in their turn cooperating with a further movable rack.

In contrast to telescopic hydraulic lifters, with the aid of the lifting device provided by the invention it is also possible to lift from the actual plane wherein the lifting device itself is located. With specially chosen cog wheel diameters and rack lengths it is even possible to lift from a plane lying below the lifting device.

In addition, only a small quantity of hydraulic fluid is necessary for using a simple hydraulic unit as provided by the invention, in contrast to telescopic hydraulic lifters. For this reason only a very small pressure fluid container is necessary, and this means some economy of space. Also less importance attaches to the pumping speed of the pressure fluid pump than to its capacity for increasing pressure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side-view, partly in section, of a lifting device provided by the invention, with the carrier device in a lowermost position;

FIG. 2 is a section view through the device on line IlIl in FIG. 1;

FIG. 3 is a side-view of the device on a smaller scale, with a treatment chair on the carrier device, raised to the upper position.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT As seen from the drawings, which show an embodiment with speed-up gear means for the lifting movement, the lifting device provided by the present invention comprises essentially a hydraulic unit 1 with a piston rod 2 and a transmission device, consisting partly of a transverse shaft 3 rotatably mounted on the top end of the piston rod 2 (see FIG. 2), two cog wheels 4,5 of different diameters firmly affixed to this shaft 3, a fixed rack 6 (see FIGS. 1 and 2) wherein the smaller cog wheel 5 engages; and a vertically movable rack 7 wherein the larger cog 4 engages. The rack 7 movable relative to the ground plane, is affixed to carrier means 8 movable in a vertical direction along a guide rail 9. On a support bracket 10 projecting from the carrier means 8 is disposed a treatment chair 11 (see FIG. 3). The stool or chair is consequently also vertically movable, which considerably facilitates the treatment of a patient in this chair. I

From the constructional aspect the present device is mounted on a ground framework 12 with two outwardly directed supports 13, by which the lifting device with the treatment chair and the patient being treated are kept in a stable position without needing bolting to the floor. The hydraulic unit 1 is mounted partly inside the ground framework 12 to insure the lowest possible construction height and the pressure cylinder 14 of the hydraulic unit is threaded into the ground framework 12. On the ground framework 12 rests a vertical support frame 15 afiixed to the ground framework by a base plate 16. In general the support frame 15 comprises an I-beam whose one transverse member is formed as a guide rail 9. The fixed rack 6 is affixed vertically by bolts 18 to the other transverse member 17 of this l-beam, and to the web 19 of the I- beam there is affixed by bolts 20 a vertical guide rail 21 along which rolls the guide roller 22 rotatably mountedat one end of the transverse shaft 3. This provides opposition to the force which tends to take cog wheel 5 out of engagement with the fixed rack 6 when the carrier means is: raised. In order to oppose the corresponding forces arising between the larger cog wheel 4 and the rack 7 movable relative to the ground plane, there is affixed to the other transverse member 17 of the beam, by means of an angular bracket 23,24, a vertical guide rail 25 along which rolls a guide roller 26 rotatably mounted at the other end of the transverse shaft 3. The two cog wheels 4,5 are affixed to the transverse shaft 3 by wedges 27,28, and the shaft 3 is rotatably mounted in a bushing 29 at the upper end of piston rod 2 (see FIG. 2). On movement of the piston rod 2 the cog wheels 4,5 therefore turn in the same direction and at the same rotary speed.

The carrier means 8 is formed as a U-shaped trolley 30 whose two arms 31,32 laterally surround the guide rail 9. Four track wheels 33-40 are rotatably mounted on axial journals 33' on these arms 31,32. The track wheels are provided with conical support surfaces 41 whereby they roll along inclined edge surfaces 42,43 of the guide rail 9, forming an acute angle with each other. This provides effective support in all directions, which is very necessary, since the forces arising between the larger cog wheel 4 and the cog wheel 7 disposed on the carrier means 8 tend to force the trolley 30 out of position. As shown for example in FIG. 2, the guide rail 9 is releasably affixed by bolts 44 to the l-beam, so that the rail is easier to machine during its manufacture.

The procedure during lifting by means of a lifting device in accordance with the present invention will be summarized below.

An electrically driven fluid pump 45 (see FIG. 3) is started by means of a switch, not shown in the drawings, so that pressure fluid flows from a container 46 through a conduit 47 and is fed to the pressure cylinder 14 of hydraulic unit 1. The fluid pressure forces upwards, in pressure cylinder 14, a piston 49 with a seal 48, whereby the piston rod 2 rigidly affixed to the piston is also forced upwards, together with the transverse shaft 3 rotatably mounted on its upper end. Engagement of the smaller cog wheel 5 in the fixed rack 6 causes a rotary movement of the transverse shaft, counterclockwise as seen in FIGS. 1 and 3, whereby the large cog wheel 4 fixedly attached to said shaft is rotated in the same direction and with the same rotational speed as the smaller cog wheel 5, but with higher peripheral speed.

The rack 7 movable relative to the plane of the ground is thus forced upwards by the larger cog wheel 4 engaged therewith, so that the carrier means 8 fixedly attached to rack 7 is moved upwardly, together with the carrier bracket 10 and treatment chair 11. Because of the higher peripheral speed of the larger cog wheel as compared with the smaller, the movable rack 7 and hence also the treatment chair 1] are given a greater lifting speed than the piston rod 2 in hydraulic unit 1, so that a greater distance of lift is achieved during the same period of time. The treatment chair 1] can be stopped at any desired level by cutting off the electrical current from the fluid pump 45, and valves known per se, e.g. non-retum valves, prevent the pressure fluid flowing out of cylinder 14. When the treatment chair 1] is lowered from one position to another, the valves are preferably opened manually, so that pressure fluid flows back out of pressure cylinder 14 into the fluid container 46.

The above is only to be considered as one example of the invention, which can be changed in various ways within the scope of the following claims. The carrier means for instance may be of different form and be fitted with guide means other than the wheels described above, and the guide rails and guides rollers may be arranged in other ways to withstand unwanted forces on the transverse shaft. Finally the support frame and the guide rail may form an integral piece.

Whatl claim is:

l. A lifting device comprising, a hydraulic cylinder having a fluid-actuated piston reciprocable therein for linear travel, transmission means for converting reciprocable linear travel of said piston into rotary motion, said transmission means comprising two rotatable elements mounted on said piston for axial travel therewith and rotatable in one direction in response to the axial travel of said piston in one direction and rotatable in an opposite direction of rotation when the piston travels in an opposite direction of axial travel, means in said transmission means including rotational means rotationally connecting said two rotary elements for driving the two rotary elements at a common speed, one of said rotary elements having a larger periphery and thereby a greater peripheral speed, means in said transmission means effective to cause said rotary elements to travel at the 7 same speed of rotation in response to the axial travel of said piston in opposite directions, carrier means coupled to said rotary element having the greater peripheral speed and travelling a greater distance than the travel of said piston in response to said greater peripheral speed, and coupling means in said transmission means coupling said carrier means to said rotary element having the greater peripheral speed and converting the rotary travel of the last-mentioned rotary element to linear travel thereby to move said carrier linearly in opposite directions when said piston is reciprocatedjn opposite directions. 2. A ll ting device according to claim 1, m which the means in the transmission means effective to cause said rotary elements to travel at the same speed of rotation and said rotational means are disposed to coact with said two rotary elements to drive the two rotary elements in the same direction of rotation when the piston travels in one axial direction and in a same opposite direction when the piston travels in an opposite axial direction.

3. A lifting device according to claim 2, in which said rotary elements are two cog wheels and in which the means effective to cause said rotary elements to travel at the same speed of rotation comprises a fixed gear rack.

4. A lifting device according to claim 1, in which said coupling means comprises means effecting travelling lineraly of said carrier means in the same general opposite directions as said piston.

5. A lifting device according to claim 4, in which said carrier means comprises means to support a human being thereon for lifting the human being to different heights, and means to supply fluid to said hydraulic cylinder to effect travel of said piston to controllably determine said different heights.

6. A lifting device according to claim 4, in which said rotary elements comprise cog wheels and in which said coupling means comprises a movable gear rack.

7. A lifting device according to claim 4, in which said carrier means is guided for linear travel, means guiding the support means for axial travel in the same general directions as said piston, and means balancing forces developed in lifting a weight supported on said carrier means.

8. A lifting device according to claim 7, in which said means to balance said forces comprises a plurality of rotatably mounted rollers travelling with said carrier means during its linear travel, and a vertical guide rail having inclined surfaces engaged by said rollers.

=k IF 

1. A lifting device comprising, a hydraulic cylinder having a fluid-actuated piston reciprocable therein for linear travel, transmission means for converting reciprocable linear travel of said piston into rotary motion, said transmission means comprising two rotatable elements mounted on said piston for axial travel therewith and rotatable in one direction in response to the axial travel of said piston in one direction and rOtatable in an opposite direction of rotation when the piston travels in an opposite direction of axial travel, means in said transmission means including rotational means rotationally connecting said two rotary elements for driving the two rotary elements at a common speed, one of said rotary elements having a larger periphery and thereby a greater peripheral speed, means in said transmission means effective to cause said rotary elements to travel at the same speed of rotation in response to the axial travel of said piston in opposite directions, carrier means coupled to said rotary element having the greater peripheral speed and travelling a greater distance than the travel of said piston in response to said greater peripheral speed, and coupling means in said transmission means coupling said carrier means to said rotary element having the greater peripheral speed and converting the rotary travel of the last-mentioned rotary element to linear travel thereby to move said carrier linearly in opposite directions when said piston is reciprocated in opposite directions.
 2. A lifting device according to claim 1, in which the means in the transmission means effective to cause said rotary elements to travel at the same speed of rotation and said rotational means are disposed to coact with said two rotary elements to drive the two rotary elements in the same direction of rotation when the piston travels in one axial direction and in a same opposite direction when the piston travels in an opposite axial direction.
 3. A lifting device according to claim 2, in which said rotary elements are two cog wheels and in which the means effective to cause said rotary elements to travel at the same speed of rotation comprises a fixed gear rack.
 4. A lifting device according to claim 1, in which said coupling means comprises means effecting travelling lineraly of said carrier means in the same general opposite directions as said piston.
 5. A lifting device according to claim 4, in which said carrier means comprises means to support a human being thereon for lifting the human being to different heights, and means to supply fluid to said hydraulic cylinder to effect travel of said piston to controllably determine said different heights.
 6. A lifting device according to claim 4, in which said rotary elements comprise cog wheels and in which said coupling means comprises a movable gear rack.
 7. A lifting device according to claim 4, in which said carrier means is guided for linear travel, means guiding the support means for axial travel in the same general directions as said piston, and means balancing forces developed in lifting a weight supported on said carrier means.
 8. A lifting device according to claim 7, in which said means to balance said forces comprises a plurality of rotatably mounted rollers travelling with said carrier means during its linear travel, and a vertical guide rail having inclined surfaces engaged by said rollers. 